British military aviation started on 10 September 1907 when the British Army
Dirigible (steerable airship) No.1 'Nulli Secundus' makes its first flight at
Farnborough. Other significant dates include:

16 October 1908, British Army Aeroplane No.1 is flown (By an American -
Samuel Franklin Cody).

28 February 1911 - An Army Order is signed, authorising the formation of
the Air Battalion of the Royal Engineers.

13 April 1912 - The Royal Flying Corps is formed. Constituted by Royal
warrant it is to include a naval wing, military wing, a central flying school
at Upavon and an aircraft factory at Farnborough.

1 July 1914 - the naval wing of the RFC was re-formed as the Royal Naval
Air Service.

1 April 1918 - The RFC and RNAS were combined to form the RAF

1 April 1924. The Fleet Air Arm of the Royal Air Force was formed under
mixed Air Ministry and Admiralty control.

24 May 1939 Admiralty re-gained full control of naval aviation which
officially became the Air Branch of the Royal Navy. However the name Fleet Air
Arm stuck, and was officially adopted in 1953.

The following text comes from the
RAF website, with
comments in square brackets.

The origins of the Royal Air Force roundel come from the First World War. The
need to be able to identify aircraft soon became apparent and orders were issued
at the end of August 1914 for the Union Flag to be painted on the under-surface
of the lower wings. [Cochrane & Elliott (1998)
show only a flag only on the rudder on 14 August at
this page and also
on the fuselage and wing since 26 October at
this page.] This
was satisfactory at low level but was confusing when the aircraft was higher as
only the cross was visible. This was often mistaken for a German cross so the
French system of concentric circles was adopted in October 1914. The main
differences between the French and British systems was that the colours were
reversed to read blue, white and red and the Union Flag was retained in
miniature between the circles and the wing tips. This miniaturised Union Flag
was also painted on the rudder.....The Union Flag on the rudder was replaced by
red, white and blue stripes in May 1915 and in June of the same year, the
Roundel, or 'Target' as it was now known, was painted on the top surface of the
upper wings. The Union Flag on the aircraft was abolished altogether. [Cochrane
& Elliott (1998) show an image at
this page as
1915-1937. This is what later became known as RAF type A roundel - see
this image.]

Aircraft of the Naval Wing of the Royal Flying Corps were marked with one red
ring and the Union Flag. [Cochrane & Elliott (1998)
show it in this page
as Dec. 1914 - May 1915].

Since the Second World War the red disk of British aircraft markings has had a
larger diameter, measuring half again the width of either of the outer rings.
The reason for this change is obscure, but it may be fair to presume a mere
technicality of draughtsmanship when the white was removed before the war, as a
concession to camouflage and then reintroduced after the war. There were
variations of the Royal Air Force roundel during the War. A fourth colour,
yellow, was added to the outside of the blue circle to make the roundel more
visible against the newly introduced camouflage schemes. Fighter aircraft in the
early years had a yellow circle of about the same thickness of the red and white
circles, whereas larger aircraft such as bombers had a much thinner yellow
circle around the roundel. [Cochrane & Elliott (1998)
report all these variations at
this page as
1937-1942 and this
page as 1942-1947. A regular roundel with a yellow border is known as type
A1 in this
image. The no-white roundel and fin flash is known as RAF type B in
this image,
and the thin white roundel is known as Type C in
this image
(with yellow ring it is called Type C1 - see
this image).
Planes could carry markings from various types at the same time. Each type has
its own fin flash].

Aircraft involved operations in the Far East carried a completely different
version altogether. Here, the roundel was of two colours only - a mid-blue/grey
outer ring with a white centre. These were carried to avoid confusion with
Japanese aircraft which carried a red circle in the centre of a thin white outer
ring. [Cochrane & Elliott (1998)
show two phases. The first is reported on
this page with
an appropriate fin flash later to be changed by replacing the inner disc to
white and adding bars - see
this page.]

Today, the roundel appears in three formats on RAF aircraft. Attack aircraft
such as Tornados and Jaguars, Chinooks, Pumas and Merlins of the Support
Helicopter Force and Hercules transports carry a two-colour roundel of dark blue
outer circle with a red centre. Fighter aircraft (Tornado F3s and Eurofighters)
and Nimrod maritime patrol aircraft carry a 'washed out' roundel of pale blue
and red whilst the traditional blue, white and red roundel can still be found on
VIP aircraft (BAe 125s and BAe146s of No 32 Squadron), Tristars and training
aircraft. [Cochrane & Elliott (1998)
show type A as
1947-1972, which is a mistake since
this type is used also today. They also show
type B as 1972-onward
and type B (low-viz)
as 1985-onward. See photos of Type A at
this
image, Type B at
this image
and low-viz at
this
image].